Renewing a 1 year membership that ends on 12/31/2011 extends it to 12/31/2013

Drupal 6 / CiviCRM 4.1

Setup: I have 1 year fixed memberships that go between 1/1 to 12/31. After importing the baseline memberships for 2011, I was starting to manually run through renewals.

Renewing a membership that ended on 12/31/2011 caused the new end date to be 12/31/2013 instead of 12/31/2012. The renewal date has no effect (I tried today, 1/1/2012, and a date in 2011).

What I did find changed things is if I updated the membership end date to 12/30/2011 and then did a renewal, which would correctly end at the end of 2012. So this seems to be an issue with determining which year 12/31 exists in during renewal, which seems to be rolling it into the next year, probably due to some bad rounding.

Note: I attempted to replicate on the demo site, however it's completely in French at the moment, and I can't seem to switch it back.